Procedure for operating an internal combustion engine and device for the execution of the procedure

ABSTRACT

Suggested is a procedure for operating a combustion engine ( 10 ), which comprises at least one pencil-type glow plug ( 12 ) that is assigned to at least one cylinder ( 11 ), and in whose exhaust gas area ( 13 ) at least one catalytic converter ( 14 ) is arranged, as well as a device for implementing the procedure. The pencil-type glow plug ( 12 ) is operated at least temporarily independent of the combustion engine operating status until reaching a preset measure for the conversion capability of the catalytic converter ( 14 ). The procedure according to the invention enables a low-emission operation of the combustion engine ( 10 ) simultaneously with minimal energy consumption and an extended lifetime of the pencil-type glow plug ( 12 ).

This application is claims benefit of Serial No. 102008 043 025.0, filed21 Oct. 2008 in Germany and which application is incorporated herein byreference. To the extent appropriate, a claim of priority is made to theabove disclosed applications.

TECHNICAL FIELD

The invention is based on a procedure for operating a combustion engineas well as on a device for implementing the procedure according to thecategory of the independent claims.

Subject matter of the present invention is also a control unit programas well as a control unit program product.

BACKGROUND

DE 10 2005 061 878 A1 describes a glow current control device forcontrolling the glow current of a pencil-type glow plug that is arrangedin a cylinder of a combustion engine. The familiar glow current controldevice comprises an environment detection device as well as a driverand/or vehicle detection device, which detect a momentary environment ofthe environmental information concerning the vehicle as well as internalinformation concerning the driver or the vehicle and send those to aperformance requirement pre-determination device. The performancerequirement pre-determination device determines an expected performancerequirement of the combustion engine, so that a previous heating of thepencil-type glow plug is possible if the combustion engine is cooleddown. Thereby the combustion in the cylinders of the combustion enginecan be improved and in particular the emission of undesired exhaustgases can be reduced.

The invention is based on the task provided a simple procedure foroperating a combustion engine, which comprises at least one pencil-typeglow plug that is assigned to at least one cylinder, and in whoseexhaust gas area at least one catalytic converter is arranged as well asa device for implementing the procedure.

SUMMARY

The invention is based on a procedure for operating a combustion engine,which comprises at least one pencil-type glow plug, which is assigned toat least one cylinder, and in whose exhaust gas area at least onecatalytic converter is arranged. The procedure according to theinvention distinguishes itself thereby that the pencil-type glow plug isoperated at least temporarily independent of the combustion engineoperating status until reaching a preset measure for the conversioncapability of the catalytic converter.

The operation of the at least one pencil-type glow plug at leasttemporarily until reaching the measure for the conversion capability ofthe catalytic converter influences in particular the combustion of thefuel in the cylinders of the combustion engine positively, meaning thata minimum of undesired exhaust gases such as carbon monoxide andhydrocarbon are created. Thereby an optimization of the combustionengine operation can be provided focusing on low NOx emissions.

The stabilizing effect by operating the pencil-type glow plug is basedon a reduction of the ignition delay and on an improvement of thecombustion robustness by a defined pre-conditioning of the combustionchamber in the cylinders of the combustion engine.

The particularly low carbon monoxide and hydrocarbon emissions are kepton a low level over the entire lifetime of the combustion engine and thecatalytic converter.

The procedure according to the invention has in particular an effectduring the cold start of the combustion engine. Furthermore theprocedure is provided during the subsequent operation of the combustionengine preferably always when the preset measure for the conversioncapability of the catalytic converter is fallen below, for example inthe range of a boost switch off of the combustion engine.

With the procedure according to the invention the special advantages ofan efficient operation of the at least one pencil-type glow plug isthereby achieved, in that the energy supply of the pencil-type glow plugcan be turned off after reaching the preset measure for the conversioncapability of the catalytic converter, so that the pencil-type glow plugdoes not have to be operated unnecessarily and the resulting fuelconsumption is unnecessarily increased. The glow plug 12 on the one handis loaded minimally and on the other hand the energy consumption isminimized.

The determination of the measure for the conversion capability of thecatalytic converter or the determination of the reaching of theconversion capability of the catalytic converter can take place indifferent ways, whereby individual embodiments are subject matter of thedependent claims, which furthermore relate to further advantageousconfigurations and improvements of the procedure according to theinvention.

A simple configuration provides that the preset measure for theconversion capability of the catalytic converter shall be reached whenthe catalytic converter has reached its start up temperature. Thestartup temperature, which is also called “light-off” temperature, isthe temperature, from which on the catalytically supported reactions cantake place in the catalytic converter in order to achieve a conversioncapability above 50%.

A particularly simple configuration provides that the preset measure forthe conversion capability of the catalytic converter shall be reachedwhen a preset operating time of the pencil-type glow plug has elapsed.

Another simple configuration provides that the preset measure for theconversion capability of the catalytic converter shall be reached whenthe catalytic converter has reached a certain conversion rate. Theconversion rate can for example be determined with the aid of an exhaustgas sensor, which is arranged downstream after the catalytic converterand which detects one or several exhaust gas components that areconverted by the catalytic converter, whereby the upstream occurringcorresponding exhaust gas components can either be calculated or alsomeasured.

One embodiment provides that the reaching of the preset measure for theconversion capability of the catalytic converter is determined with theaid of a comparison of the exhaust gas temperature that is measured orcalculated upstream of the catalytic converter with an upstream exhaustgas temperature threshold value.

An alternative or additional embodiment provides that the reaching ofthe preset measure for the conversion capability of the catalyticconverter is determined with the aid of a comparison of the exhaust gastemperature that is measured downstream of the catalytic converter withan downstream exhaust gas temperature threshold value.

An advantageous embodiment provides that the reaching of the presetmeasure for the conversion capability of the catalytic converter isdetermined with the aid of a comparison of the difference that occurs atthe catalytic converter between the downstream exhaust gas temperatureand the upstream exhaust gas temperature and a comparison with atemperature difference threshold, whereby the downstream exhaust gastemperature can be measured and the upstream exhaust gas temperature canbe measured or calculated.

With those measure in particular the ageing process of the catalyticconverter can be considered, during which the conversion capability ofthe catalytic converter usually diminishes.

Alternatively or additionally the reaching of the preset measure for theconversion capability of the catalytic converter can also be determinedby measuring the exhaust gas lambda downstream after the catalyticconverter and a comparison with a downstream exhaust gas lambdathreshold value.

Alternatively or additionally the reaching of the preset measure for theconversion capability of the catalytic converter can also be determinedby an occurring difference between the downstream exhaust gas lambda andthe upstream exhaust gas lambda and a comparison of the deviation withan exhaust gas lambda deviation threshold value. The exhaust gas lambdais thereby measured downstream and measured or calculated upstreambefore the catalytic converter.

The previously described embodiments, at which at least one exhaust gastemperature and/or at least one exhaust gas lambda are evaluated,qualify not only for determining the reaching of the preset measure forthe conversion capability of the catalytic converter but aresimultaneously suitable for determining whether the catalytic converterhas reached its start up temperature.

According to one improvement it is provided that the electric power thatis delivered to the pencil-type glow plug varies. At the beginning ofthe heating process for example an increased power can be preset, whichis lowered with an increasing operating time of the pencil-type glowplug.

The device according to the invention for implementing the procedurerelates initially to a customized control unit, which contains measuresfor implementing the procedure. A conversion capability determination aswell as a pencil-type glow plug heat control is provided as suchmeasures.

The control unit contains preferably at least one electric storage, inwhich the steps of the procedure are stored as control unit program.

The control unit program provides according to the invention that allsteps of the procedure are carried out if it runs in a control unit.

The control unit program product with a program code that is stored on amachine-readable medium carries out the procedure according to theinvention if the program runs in a control unit.

Embodiments of the inventions are illustrated in the drawing and furtherexplained in the subsequent description.

BRIEF DESCRIPTION OF THE DRAWING

The FIGURE shows a technical surrounding, in which a procedure accordingto the invention is carried out.

DETAILED DESCRIPTION

The FIGURE shows a combustion engine 10, which comprises at least onecylinder 11 assigned to a pencil-type glow plug 12. At least onecatalytic converter 14 is arranged in the exhaust gas area 13 of thecombustion engine 10.

In the exhaust gas area 13 upstream before the catalytic converter 14 anupstream exhaust gas temperature te_vK occurs as well as an upstreamexhaust gas lambda la_vK. Downstream after the catalytic converter 14 adownstream exhaust gas temperature te_nK as well as a downstream exhaustgas lambda lam_nK occur.

The upstream exhaust gas lambda lam_vK are measured by an upstreamlambda sensor 15 and the upstream exhaust gas temperature te_vK by anupstream temperature sensor 16. The downstream exhaust gas temperaturete_nK is measured by a downstream temperature sensor 17 and thedownstream exhaust gas lambda lam_nK by a downstream lambda sensor 18.

A control unit 20 provides the pencil-type glow plug 12 and a heatoutput HZ. The upstream lambda sensor 15 sends a measured upstreamexhaust gas lambda lam_Mes_vK, the upstream temperature sensor 16 ameasured upstream exhaust gas temperature te_Mes_vK, the downstreamtemperature sensor 17 a downstream exhaust gas temperature te_Mes_nK andthe downstream lambda sensor 17 a measured downstream exhaust gas lambdalam_Mes_nK to the control unit 20.

The control unit 20 contains a conversion rate determination 21 as wellas a pencil-type glow plug heat control 22.

The conversion rate determination 21 is provided with a maximum periodof time ti_Max, a start up temperature te_An, the measured downstreamexhaust gas temperature te_Mes_nK, a downstream exhaust gas temperaturethreshold value te_ScW_nK, the measured upstream exhaust gas temperaturete_Mes_vK, a calculated upstream exhaust gas temperature te_Sim_vK, anupstream exhaust gas temperature threshold value te_ScW_vK, atemperature difference threshold value te_Dif_ScW, the measureddownstream exhaust gas lambda lam_Mes_nK, a downstream exhaust gaslambda threshold value lam_ScW_nK, the measured upstream exhaust gaslambda lam_Mes_vK, a calculated upstream exhaust gas lambda lam_Sim_vK,an exhaust gas lambda deviation threshold value lam_Dif_ScW as well as apercentage conversion rate %. The conversion rate determination 21provides a glow demand signal Anf_Gl, which is provided to thepencil-type glow plug heat control 22, which is furthermore providedwith a combustion engine demand signal Anf_Bkm as well as a heat powerdefault var_HZ and which provides the heat output HZ for the pencil-typeglow plug 12.

The procedure according to the invention works as follows:

The catalytic converter 14 that is arranged in the exhaust gas area 13of the combustion engine 10 is provided for the conversion of undesiredexhaust gas components of the combustion engine 10 as for example carbonmonoxide, hydrocarbons and nitrous gases.

According to the invention the operation of the pencil-type glow plug 12is provided at least temporarily until the reaching of a preset measurefor the conversion capability of the catalytic converter 14, whereby atleast one pencil-type glow plug 12 is assigned to at least one cylinder11 of the combustion engine 10. An insufficient conversion capabilityoccurs in particular at a cold start of the combustion engine 10. Butthe conversion capability can also fall below the preset measure in thesubsequent operation of the combustion engine 10, for example during aboost switch off.

The pencil-type glow plug 12 is usually provided for heating theair-fuel mixture that is supplied to a diesel combustion engine 10. Thepencil-type glow plug 12 is therefore usually operated depending on theoperating status of the combustion engine 10, for example depending on acold start process. For this purpose the pencil-type glow plug heatcontrol 22 is provided with the combustion engine demand signal Anf_Bkm,which causes the pencil-type glow plug heat control 22 to provide theheat output HZ. The combustion engine demand signal Anf_Bkm can forexample depend on the operating temperature of the combustion engine 10.

In practice the pencil-type glow plug 12 is connected to a not furthershown, if necessary periodical voltage source, whereby the currentdepends on the pencil-type glow plug temperature.

The controlling of the pencil-type glow plug 12 independent of thecombustion engine operating status at least temporarily until reachingthe preset measure for the conversion capability of the catalyticconverter 14 takes place depending on the glow demand signal Anf_Gl,which is provided by the conversion rate determination 21. Thepencil-type glow plug 12 can thereby be impinged with the heat output HZat least temporarily until reaching the preset measure for theconversion capability of the catalytic converter 14 independent of thecombustion engine demand signal Anf_Bkm.

By operating the pencil-type glow plug 12 the exhaust gas raw emissionof the combustion engine, in particular the carbon monoxide emission andthe hydrocarbon emissions are positively influenced, so that even in thecase of an insufficient conversion capability of the catalytic converter14 minimal emissions occur. By heating the pencil-type glow plug 12electric energy is inserted into the cylinder 11 of the combustionengine 10, which contributes to a temperature increase in the cylinder11 and therefore also in the exhaust gas area 13, whereby the heating ofthe catalytic converter 14 can be supported. A heating requirement ofthe catalytic converter 14 can thereby exist based on a cold start ofthe combustion engine 10 as well as on a combustion engine operationstatus with a low upstream exhaust gas temperature te_vK, as for examplein idle status or in the range of a boost switch off of the combustionengine 10.

According to a simple embodiment the preset measure for the conversioncapability of the catalytic converter 14 is reached, when the presetmaximum period of time ti_Max has elapsed. The beginning of the timeperiod can for example be determined by a not further shown demand forheating the catalytic converter 14. The beginning of the time period canfurthermore be determined depending on measures that are describedfurther below.

According to another very simple embodiment the reaching of the presetmeasure for the conversion capability of the catalytic converter 14 isassumed when the catalytic converter 14 has achieved a start uptemperature te_An. The reaching of the startup temperature te_An canalso be determined by measures that are described further below.

According to an alternative simple embodiment it can be provided thatthe preset measure for the conversion capability of the catalyticconverter 14 should be reached, when the catalytic converter has reacheda certain conversion rate %. In this embodiment a specific percentage,for example 80% can be preset, whereby the reaching of the specificconversion rate % can be determined by a not further shown exhaust gassensor that is arranged downstream after the catalytic converter 14 anda comparison with the converted exhaust gas component that has beenmeasured or calculated upstream before the catalytic converter.

A further embodiment provides that the reaching of the preset measurefor the conversion capability of the catalytic converter 14 isdetermined with the of a comparison of the measured downstream exhaustgas temperature te_Mes_nK with the downstream exhaust gas temperaturethreshold value te_ScW_nK. The downstream exhaust gas temperature te_nKcan be used as an approximate measure for the temperature of thecatalytic converter.

Alternatively or additionally it can be provided that the reaching ofthe preset measure for the conversion capability of the catalyticconverter 14 is determined with the aid of a comparison of the measuredupstream exhaust gas temperature te_Mes_vK with the upstream exhaust gastemperature threshold value te_ScW_vK. In that case the upstream exhaustgas temperature te_vK is used as an approximate measure for thetemperature of the catalytic converter.

According to another approach that can be provided additionally oralternatively the reaching of the preset measure for the conversioncapability of the catalytic converter 14 is determined with the aid of acomparison of the difference that occurs at the catalytic converter 14between the downstream exhaust gas temperature te_nK and the upstreamexhaust gas temperature te_vK and a comparison with the temperaturedifference threshold value te_Dif_ScW, whereby the downstream exhaustgas temperature te_nK can be measured and the upstream exhaust gastemperature te_vK can be measured or calculated.

The upstream exhaust gas temperature te_vK can be provided to theconversion capability determination 21 as a measured upstream exhaustgas temperature te_Mes_vK as well as a calculated upstream exhaust gastemperature te_Sim_vK. The calculated upstream exhaust gas temperaturete_Sim_vK can for example be calculated depending on variables of thecombustion engine 10 such as the load or the fuel amount that has beenintroduced into the combustion engine 10.

The embodiments that are based on the detection of at least one exhaustgas temperature cannot only be used for determining the preset measurefor the conversion capability of the catalytic converter 14 but also fordetermining the reaching of its start up temperature.

Alternatively or additionally the preset measure for the conversioncapability of the catalytic converter 14 can be determined by acomparison between the measured downstream exhaust gas lambda lam_nK andthe downstream exhaust gas lambda threshold value lam_ScW_nK.

It is especially advantageously that the reaching of the preset measurefor the conversion capability of the catalytic converter 14 canadditionally or alternatively be determined by a comparison of thedownstream exhaust gas lambda lam_nK with the upstream exhaust gaslambda lam_vK. The upstream exhaust gas lambda lam_vK can thereby beprovided by the measured upstream exhaust gas lambda lam_Mes_vK or bythe calculated upstream exhaust gas lambda lam_Sim_vK. The reaching ofthe preset measure for the conversion capability of the catalyticconverter 14 is subsequently determined by comparing the measureddownstream exhaust gas lambda lam_Mes_nK with the measured upstreamexhaust gas lambda lam_Mes_vK or the calculated upstream exhaust gaslambda lam_Sim_vK. The difference is compared to the exhaust gas lambdadeviation threshold value lam_Dif_ScW, whereby the values of thedeviations of the exhaust gas lambdas lam_vK, lam_nK can preferably betaken as a basis for the comparison. It is thereby assumed that in thecase of reaching the preset measure for the conversion capability of thecatalytic converter 14 the exhaust gas lambda deviation threshold valuelam_Dif_ScW is exceeded. Because the upstream exhaust gas lambda lam_vKcan vary above as well as below the stoichiometric exhaust gas lambdathe value creation of the exhaust gas lambda deviation is preferablyprovided.

According to one embodiment a power control of the pencil-type glow plug12 can be provided with the aid of a heat output default var_HZ. Theinfluencing of the power takes preferably place in such a way that atthe beginning of the heating of the pencil-type glow plug 12 the maximumpower is preset while it is reduced with an increasing operating time ofthe pencil-type glow plug 12. The described approaches according to theinvention enables a targeted switching off of the heating of thepencil-type glow plug 12 at a point of time, at which the catalyticconverter 14 is able to ensure a sufficient conversion of undesiredexhaust gas components, so that an optimization of the emissions of thecombustion engine 10 by operating the pencil-type glow plug 12 withinthe scope of the invention's measures can fade into the background.Thereby the pencil-type glow plug 12 is minimally burdened on the onehand and the energy consumption minimized on the other hand.

1. A procedure for operating a combustion engine, which comprises atleast one pencil-type glow plug that is assigned to at least onecylinder, and in whose exhaust gas area at least one catalytic converteris arranged, wherein the pencil-type glow plug is operated at leasttemporarily independent of the combustion engine operating status untilreaching a preset measure for the conversion capability of the catalyticconverter.
 2. The procedure according to claim 1, wherein the presetmeasure for the conversion capability of the catalytic converter, if thecatalytic converter has reached its start up temperature.
 3. Theprocedure according to claim 1, wherein the preset measure for theconversion capability of the catalytic converter is reached, when apreset operating time of the pencil-type glow plug has elapsed.
 4. Theprocedure according to claim 1, wherein the preset measure for theconversion capability of the catalytic converter is reached when thecatalytic converter has reached a certain conversion rate.
 5. Theprocedure according to claim 1, wherein the reaching of the presetconversion capability of the catalytic converter is determined with theaid of a comparison of the upstream exhaust gas temperature that hasbeen measured or calculated upstream of the catalytic converter with anupstream exhaust gas temperature threshold value.
 6. The procedureaccording to claim 1, wherein the reaching of the preset measure for theconversion capability of the catalytic converter is determined with theaid of a comparison of the downstream exhaust gas temperature that hasbeen measured or calculated downstream of the catalytic converter withan downstream exhaust gas temperature threshold value.
 7. The procedureaccording to claim 1, wherein the reaching of the preset measure for theconversion capability of the catalytic converter is determined with theaid of a comparison of the difference that occurs at the catalyticconverter between the downstream exhaust gas temperature and theupstream exhaust gas temperature and a comparison of the temperaturedifference threshold value, wherein the downstream exhaust gastemperature is measured and the upstream exhaust gas temperature ismeasured or calculated.
 8. The procedure according to claim 1, whereinthe reaching of the preset measure for the conversion capability of thecatalytic converter is determined with the aid of a comparison of thedownstream after the catalytic converter measured downstream exhaust gaslambda and a comparison with a downstream exhaust gas lambda thresholdvalue.
 9. The procedure according to claim 1, wherein the reaching ofthe preset measure for the conversion capability of the catalyticconverter is determined with the aid of an occurring difference betweenthe downstream exhaust gas lambda and the upstream exhaust gas lambdaand a comparison with an exhaust gas lambda threshold value, wherein thedownstream exhaust gas lambda is measured and the upstream exhaust gaslambda is measured or calculated.
 10. The procedure according to claim1, wherein the temperature of the pencil-type glow plug varies.
 11. Adevice for operating a combustion engine, which comprises at least onepencil-type glow plug that is assigned to at least one cylinder, and inwhose exhaust gas area at least one catalytic converter is arranged,wherein at least one customized control unit is provided forimplementing the procedure according to one of the previous claims,which contains measures for implementing the procedure.
 12. A controlunit program, which carries out all steps of a procedure according toclaim 1 if the program runs in a control unit.
 13. A control unitprogram product with a program code that is stored on a machine-readablemedium for implementing the procedure according to claim 1 if theprogram is carried out in a control unit.